To use the Consumer Price Index for a real adjustment, you pick the CPI series your situation calls for, look up two unadjusted index values from the Bureau of Labor Statistics for the months your contract or program specifies, calculate the percentage change between them, and multiply the payment by one plus that percentage. The rest is knowing which series to pick and how to write the clause so both sides get the same answer.
Pick the Right CPI Series
The BLS publishes several consumer price indexes, and they don’t move at identical rates. Choosing the wrong one produces a defensible-looking number that’s still wrong for your purpose.
The CPI for All Urban Consumers (CPI-U) covers more than 90 percent of the U.S. population and is the default for most commercial leases and salaried employment agreements. The CPI for Urban Wage Earners and Clerical Workers (CPI-W) covers roughly 30 percent of the population, limited to households where most income comes from hourly or clerical work, and it’s the index Social Security uses for its annual cost-of-living adjustment.1U.S. Bureau of Labor Statistics. Consumer Price Indexes Overview2GovInfo. 20 CFR 404.272 – Indexes We Use to Measure the Rise in the Cost-of-Living The Chained CPI for All Urban Consumers (C-CPI-U) accounts for the way people substitute cheaper goods when prices rise, so it grows a bit slower than the CPI-U. Congress chose it for federal income tax bracket adjustments under the Tax Cuts and Jobs Act.3U.S. Bureau of Labor Statistics. Chained Consumer Price Index Questions and Answers4Office of the Law Revision Counsel. 26 U.S. Code 1 – Tax Imposed
Unadjusted, Not Seasonally Adjusted
Each month the BLS releases both a seasonally adjusted and an unadjusted CPI figure. For any escalation clause, pension formula, or collective bargaining agreement, use the unadjusted series. The BLS itself recommends this because seasonally adjusted numbers are revised each year when the agency updates its seasonal factors, so a figure you locked in this January could change the following January. Unadjusted numbers are final once published.5U.S. Bureau of Labor Statistics. Using Seasonally Adjusted and Unadjusted Data
National or Regional
The BLS also publishes CPI data for the four census regions and about two dozen metropolitan areas including New York, Los Angeles, Chicago, and Houston.6U.S. Bureau of Labor Statistics. Regional Resources A national employer typically references the national CPI-U; a landlord in Miami might tie rent to the Miami-area CPI. Metro-area indexes are published less frequently, some only every other month, so a contract keyed to a regional index needs to say what happens in a month when no data is released.
Pull the Numbers From BLS
All CPI data comes from the BLS website. The databases page lets you pull specific series by geography and month; if your lease uses the January-to-January change in the national CPI-U (all items, unadjusted), you look up that series and record both January index values.7U.S. Bureau of Labor Statistics. Consumer Price Index Databases
Every CPI figure is expressed relative to a base period. For the current series, the 1982–1984 average equals 100, so a February 2026 reading of 326.785 means a basket that cost $100 in the base period now costs about $326.79.8U.S. Bureau of Labor Statistics. Table 1 – Consumer Price Index for All Urban Consumers
For a quick personal check on what a past dollar amount is worth today, the BLS inflation calculator does the arithmetic for you.9U.S. Bureau of Labor Statistics. CPI Inflation Calculator For a contract adjustment, pull the raw numbers and run the formula yourself so every step is documented.
Calculate the Percentage Change
Subtract the earlier index value from the later one, divide by the earlier value, and multiply by 100.
Using the unadjusted CPI-U for all items: 319.082 in February 2025 and 326.785 in February 2026.8U.S. Bureau of Labor Statistics. Table 1 – Consumer Price Index for All Urban Consumers
- 326.785 − 319.082 = 7.703
- 7.703 ÷ 319.082 = 0.02414
- 0.02414 × 100 = 2.4 percent
A positive result means prices rose. A negative result, rare but possible, means prices fell and purchasing power rose. Precision matters. Rounding too early or slipping a decimal cascades through every dollar amount you adjust, and on a large commercial lease a tenth of a percentage point can be thousands of dollars a year.
Apply the Change to a Payment
Multiply the current payment by (1 + the percentage as a decimal). If rent is $5,000 a month and CPI rose 2.4 percent, the new rent is $5,000 × 1.024 = $5,120.
Social Security works the same way on a larger scale. Each year the Social Security Administration compares the average CPI-W for the third quarter of the current year against the third quarter of the prior base, and if prices rose, benefits go up by the same percentage the following January.10Office of the Law Revision Counsel. 42 U.S. Code 415 – Computation of Primary Insurance Amount For January 2026, that adjustment was 2.8 percent, so a retiree who received $2,000 a month in 2025 now receives $2,056.11Social Security Administration. Cost-of-Living Adjustment Information
For personal budgeting the arithmetic is identical. If your household costs tracked the overall CPI last year, you need about 2.4 percent more income to stand still.
Write the Clause Carefully
A well-drafted CPI escalation clause names five things: the specific index (for example, CPI-U, all items, U.S. city average), whether the data is unadjusted, the exact months being compared, the geographic scope, and any cap or floor on the resulting increase.
Caps and floors are where negotiation matters. A cap limits how much rent or wages can rise in a single year regardless of what the CPI does, protecting the paying side from a spike. A floor guarantees a minimum increase even if inflation is flat or negative. A common structure sets a floor at 2 percent and a cap at 4 or 5 percent. Without a cap, an unexpected inflation year can overrun an operating budget; without a floor, the receiving side absorbs rising costs with no relief.
Vague language invites disputes. “Adjusted annually for inflation” doesn’t identify a single number either party can verify independently. A workable clause reads more like: “Effective each January 1, base salary shall increase by the percentage change in the unadjusted CPI-U (all items, U.S. city average) from October of the prior year to October of the current year.”
Two more details are easy to miss. First, state whether the adjustment compounds. A compounding clause applies each year’s increase to the already-adjusted amount, so the base keeps growing; a non-compounding clause applies each year’s percentage to the original starting figure, producing smaller raises over time. Over a multi-year contract the two methods diverge substantially. Second, plan for a data gap. The BLS noted that October 2025 CPI data was unavailable due to a lapse in federal appropriations.8U.S. Bureau of Labor Statistics. Table 1 – Consumer Price Index for All Urban Consumers A fallback provision, using the most recently published index or a named substitute, keeps a missing month from becoming a dispute.
A Note on the CPI for Older Americans
If you’re planning retirement income, you may see references to the CPI-E, an experimental index the BLS has published that re-weights the basket to reflect the spending of Americans aged 62 and older. Medical care carries roughly double the share it holds in the CPI-W, and shelter carries a larger weight as well.12Bureau of Labor Statistics. The Experimental Consumer Price Index for Elderly Americans (CPI-E): 1982-2007 Because healthcare and housing have historically risen faster than the overall basket, the CPI-E tends to grow faster than the CPI-W. It remains experimental and is not used for Social Security or any other official adjustment, so you can’t apply it to a benefit calculation, but it’s a reference point if you suspect the standard COLA understates the inflation you actually see.